Annotation tools in Revit include:
Dimensions
Text
Measurement tags for levels, coordinates and slopes
Identification tags
All can be found under the Annotate tab.
Note that all annotation except text can't exist on their own. They have to be associated with something in the model.
And if the thing they are associated with is delete they delete themselves, if things they are associated with are hidden they will also be hidden.
DIMENSIONING
Dimension tools include methods to measure distance, angles and curves.
The Align tool is best to use for distances, it measures between anything, whereas the Linear tool only measures between points.
Dimensions in Revit can only measure something that exists. You can't create dimensions to arbitrary points. And dimensions must mean something. For example you can't place a dimension between two non-parallel walls (or non-parallel grid) because the dimension varies between them. You can however dimension between end points.
Walls are the most commonly thing dimensioned and you can dimension from:
Face of wall
Centre of wall
End point of wall
Cores of wall (either side of structure, depending on how wall was created - e.g. studs)
To dimension you select a dimension tool, then the objects you want to dimension between.
Use the Tab key to cycle through objects and things you can dimension to.
Select the first line or point, then the second. The dimension will appear. Move your mouse to the place you want the dimension to be place, if you are finished pick anywhere there are no objects, if you want a line of dimensions not pick the next line or point (use Tab key to cycle through what to pick), repeat till done.
You can set the default thing selected via the list box in the green options bar (in this case Wall faces).
Note that dimensions can't exist on their own. They have to be associated with something in the model.
And if the thing they are associated with is delete they delete themselves, if things they are associated with are hidden they will also be hidden.
TEXT
When you hit the Text tool the menu will change, showing options for text.
But before doing anything select the Text style you want to use.
In the Properties window click on the black triangle, then select which text style you want to use.
Back in the main menu you will see options for text.
There are different options for doing leader arrows, where those leaders are placed, and alignment and font options.
Once you select what you want just click where you want the text and start writing.
MEASUREMENT TAGS
Measurement tags show a measurement value of the thing tagged.
You can measure:
Elevation (Relative Level)
Coordinates (Easting and Northings)
Slopes & falls
SPOT ELEVATION
Spot Elevation tool places a tag showing the relative level of the point picked.
Not everything can be tagged, as some things don't have a height. For example 2D objects.
Change the tag by selecting a different type in the Properties window. Click on the black triangle then select the one you want:
SPOT COORDINATE
Spot Coordinate tool places a tag showing the survey coordinates, and depending on the tag, relative level of the point picked.
Not everything can be tagged.
Be aware that Spot Coordinates only make sense if the project has had its Survey Point set based on the surveyor's information. If it hasn't the tag will show Revit's internal XY distance from the project base point.
Change the tag by selecting a different type in the Properties window. Click on the black triangle then select the one you want:
SPOT SLOPE
Sloping surfaces can have their slope values tagged. For example floors and roofs.
Either the fall ( 1:20) or degrees (20°) can be tagged depending on the tag used.
Change the tag by selecting a different type in the Properties window. Click on the black triangle then select the one you want:
IDENTIFICATION TAGS
Although pretty much anything about an object can be tagged in Revit, a tag has to be created for each thing.
Generally you will want to tag the type code for objects (e.g. Wall Type code), or materials (e.g. the outside material of a wall).
The values in many tags can be edited, but be aware that by editing a tag you are also changing values for all types of the object the tag relates to, and any schedules those values appear in. So if you change the value of a wall code it will change that value in ALL walls of that wall type, both in tags and in schedules.
If you use Multi-Category tags you can use the same tag on everything.
After selecting the Multi-Category or Material Tag tool choose which tag to use from the Properties window.
You can control the leader in the green options bar.
You can also tag rooms:
Change the tag by selecting a different type in the Properties window. Click on the black triangle then select the one you want: